1. Field of the Invention
This invention relates a semiconductor integrated circuit device, and more particularly, it relates to an electrical connection in such circuit.
2. Description of Related Art
In most semiconductor devices of the prior art, power is transmitted from a power source on the semiconductor device or chip over a power bus A as illustrated in the prior art arrangement shown in FIG. 1. A plurality of row buses B extend perpendicularly away from the power bus A. The row buses B have a plurality of circuits or cells C which are coupled thereto and which receive current from the row bus B. As illustrated, each row bus B is coupled to the power bus A by a series of vias D.
One of the problems with this arrangement is that the current would flow primarily through the first via D-1. As more cells C were added to the row bus B, the current flowing through the first via D-1 would increase. This caused the first via D-1 to be overloaded. The other vias would become "shadowed" because the current would only flow through the first via D-1 and not the other vias. The reliability of the electrical connection between the row bus B and power bus A became highly dependent on the current conducting capacity of the first via D-1. In many instances, one or more of the cells coupled to the row bus B would malfunction or simply fail because the first via D-1 could not conduct the current required. Overloading the first via D-1 would also cause that via to "burn out". The current would then flow through the next via D-2 until all the vias D became successively overloaded and burnt out, eventually causing the row bus B to be disconnected from the power bus A.